As far as front springs, I would suggest going though Ames. Both Ames and Eaton sell the same Moog front coil springs and you might have a better chance getting the correct ones from Ames since they know pontiacs specifically. The front springs I got from Ames 15 years ago worked out pretty well on my 67 firebird vert. I had a bad time with Eaton getting the correct front springs for my 69 GTO vert. They sold me Moog springs that were comically way too tall and wouldn't believe me that they were wrong. I had to force them to take them back and send hardtop springs that were much closer to correct. So they are continuing to sell the wrong springs to unsuspecting GTO/LeMans vert customers. I'm still pissed at Eaton.

I would also suggest making sure you really need new springs before you go down this path. Changing front springs is not fun and somewhat dangerous and you could end up with a ride height you don't like.